This paper was published in the Permananet Way Institution journal in 2012 (Vol. 131 Part 3).
HOVAR looks at a route section, and determines whether each 1/16th of a mile has any constraints in it that would prohibit the use of the High Output machinery available to the track engineer.
The machinery includes the High Output Ballast Cleaner (HOBC), the Medium Output Ballast Cleaner (MOBC), and the Track Renewal Train (TRT).
The constraints invovled are: platforms, underbridges and tunnels, S&C, steel sleepers, wooden sleepers, and level crossings.
Recent trials (2013) carried out not long after this paper was published determined that steel sleepers could potentially be ballast cleaned, therefore this constraint could now be remvoed. However, it is suggested that it is noted and reviewed on a site by site basis.